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Lambda Expressions

Lambda expressions are anonymous functions which are passed as arguments to higher-order SQL functions.

Lambda expressions are written with -> : 

x -> x + 1
(x, y) -> x + y
x -> regexp_like(x, 'a+')
x -> x[1] / x[2]
x -> IF(x > 0, x, -x)
x -> COALESCE(x, 0)
x -> CAST(x AS JSON)
x -> x + TRY(1 / 0)

Limitations

Limitations Examples
Subqueries are not supported x -> 2 + (SELECT 3)
Aggregations are not supported x -> max(y)

Examples

transform()

Function Description Return Type
transform() Applies a transformation function to each element of an array column. Array 
SELECT numbers,
       transform(numbers, n -> n * n) as squared_numbers
FROM (
    VALUES
        (ARRAY[1, 2]),
        (ARRAY[3, 4]),
        (ARRAY[5, 6, 7])
) AS t(numbers);

  numbers  | squared_numbers
-----------+-----------------
 [1, 2]    | [1, 4]
 [3, 4]    | [9, 16]
 [5, 6, 7] | [25, 36, 49]
(3 rows)

any_match()

Function Description Return Type
any_match() Checks if any element in an array column matches a specified condition. Boolean 
SELECT numbers
FROM (
    VALUES
        (ARRAY[1,NULL,3]),
        (ARRAY[10,20,30]),
        (ARRAY[100,200,300])
) AS t(numbers)
WHERE any_match(numbers, n ->  COALESCE(n, 0) > 100);
-- [100, 200, 300]

regexp_replace()

Function Description Return Type
regexp_replace() Performs a regular expression search and replace on a string column. String 
SELECT regexp_replace('once upon a time ...', '^(\w)(\w*)(\s+.*)$',x -> upper(x[1]) || x[2] || x[3]);
-- Once upon a time ...

reduce_agg()

Function Description Return Type
reduce_agg() Aggregates values in a column using a provided binary operation and an optional combination function for distributed processing. Depends 
SELECT reduce_agg(value, 0, (a, b) -> a + b, (a, b) -> a + b) sum_values
FROM (
    VALUES (1), (2), (3), (4), (5)
) AS t(value);
-- 15